// Copyright 2022 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

import Foundation

/**
 * `StorageReference` represents a reference to a Google Cloud Storage object. Developers can
 * upload and download objects, as well as get/set object metadata, and delete an object at the
 * path. See the Cloud docs  for more details: https://cloud.google.com/storage/
 */

@objc(FIRStorageReference) open class StorageReference: NSObject {
  // MARK: - Public APIs

  /**
   * The `Storage` service object which created this reference.
   */
  @objc public let storage: Storage

  /**
   * The name of the Google Cloud Storage bucket associated with this reference.
   * For example, in `gs://bucket/path/to/object.txt`, the bucket would be 'bucket'.
   */
  @objc public var bucket: String {
    return path.bucket
  }

  /**
   * The full path to this object, not including the Google Cloud Storage bucket.
   * In `gs://bucket/path/to/object.txt`, the full path would be: `path/to/object.txt`
   */
  @objc public var fullPath: String {
    return path.object ?? ""
  }

  /**
   * The short name of the object associated with this reference.
   * In `gs://bucket/path/to/object.txt`, the name of the object would be `object.txt`.
   */
  @objc public var name: String {
    return (path.object as? NSString)?.lastPathComponent ?? ""
  }

  /**
   * Creates a new `StorageReference` pointing to the root object.
   * - Returns: A new `StorageReference` pointing to the root object.
   */
  @objc open func root() -> StorageReference {
    return StorageReference(storage: storage, path: path.root())
  }

  /**
   * Creates a new `StorageReference` pointing to the parent of the current reference
   * or `nil` if this instance references the root location.
   * For example:
   *     path = foo/bar/baz   parent = foo/bar
   *     path = foo           parent = (root)
   *     path = (root)        parent = nil
   * - Returns: A new `StorageReference` pointing to the parent of the current reference.
   */
  @objc open func parent() -> StorageReference? {
    guard let parentPath = path.parent() else {
      return nil
    }
    return StorageReference(storage: storage, path: parentPath)
  }

  /**
   * Creates a new `StorageReference` pointing to a child object of the current reference.
   *     path = foo      child = bar    newPath = foo/bar
   *     path = foo/bar  child = baz    ntask.impl.snapshotwPath = foo/bar/baz
   * All leading and trailing slashes will be removed, and consecutive slashes will be
   * compressed to single slashes. For example:
   *     child = /foo/bar     newPath = foo/bar
   *     child = foo/bar/     newPath = foo/bar
   *     child = foo///bar    newPath = foo/bar
   * - Parameter path The path to append to the current path.
   * - Returns: A new `StorageReference` pointing to a child location of the current reference.
   */
  @objc(child:) open func child(_ path: String) -> StorageReference {
    return StorageReference(storage: storage, path: self.path.child(path))
  }

  // MARK: - Uploads

  /**
   * Asynchronously uploads data to the currently specified `StorageReference`,
   * without additional metadata.
   * This is not recommended for large files, and one should instead upload a file from disk.
   * - Parameters:
   *   - uploadData: The data to upload.
   *   - metadata: `StorageMetadata` containing additional information (MIME type, etc.)
   *       about the object being uploaded.
   * - Returns: An instance of `StorageUploadTask`, which can be used to monitor or manage the upload.
   */
  @objc(putData:metadata:)
  @discardableResult
  open func putData(_ uploadData: Data, metadata: StorageMetadata? = nil) -> StorageUploadTask {
    return putData(uploadData, metadata: metadata, completion: nil)
  }

  /**
   * Asynchronously uploads data to the currently specified `StorageReference`.
   * This is not recommended for large files, and one should instead upload a file from disk.
   * - Parameter uploadData The data to upload.
   * - Returns: An instance of `StorageUploadTask`, which can be used to monitor or manage the upload.
   */
  @objc(putData:) @discardableResult open func __putData(_ uploadData: Data) -> StorageUploadTask {
    return putData(uploadData, metadata: nil, completion: nil)
  }

  /**
   * Asynchronously uploads data to the currently specified `StorageReference`.
   * This is not recommended for large files, and one should instead upload a file from disk.
   * - Parameters:
   *   - uploadData: The data to upload.
   *   - metadata: `StorageMetadata` containing additional information (MIME type, etc.)
   *       about the object being uploaded.
   *   - completion: A closure that either returns the object metadata on success,
   *       or an error on failure.
   * - Returns: An instance of `StorageUploadTask`, which can be used to monitor or manage the upload.
   */
  @objc(putData:metadata:completion:) @discardableResult
  open func putData(_ uploadData: Data,
                    metadata: StorageMetadata? = nil,
                    completion: ((_: StorageMetadata?, _: Error?) -> Void)?) -> StorageUploadTask {
    let putMetadata = metadata ?? StorageMetadata()
    if let path = path.object {
      putMetadata.path = path
      putMetadata.name = (path as NSString).lastPathComponent as String
    }
    let task = StorageUploadTask(reference: self,
                                 service: storage.fetcherServiceForApp,
                                 queue: storage.dispatchQueue,
                                 data: uploadData,
                                 metadata: putMetadata)
    startAndObserveUploadTask(task: task, completion: completion)
    return task
  }

  /**
   * Asynchronously uploads a file to the currently specified `StorageReference`.
   * `putData` should be used instead of `putFile` in Extensions.
   * - Parameters:
   *   - fileURL: A URL representing the system file path of the object to be uploaded.
   *   - metadata: `StorageMetadata` containing additional information (MIME type, etc.)
   *       about the object being uploaded.
   * - Returns: An instance of `StorageUploadTask`, which can be used to monitor or manage the upload.
   */
  @objc(putFile:metadata:) @discardableResult
  open func putFile(from fileURL: URL, metadata: StorageMetadata? = nil) -> StorageUploadTask {
    return putFile(from: fileURL, metadata: metadata, completion: nil)
  }

  /**
   * Asynchronously uploads a file to the currently specified `StorageReference`,
   * without additional metadata.
   * `putData` should be used instead of `putFile` in Extensions.
   * @param fileURL A URL representing the system file path of the object to be uploaded.
   * @return An instance of StorageUploadTask, which can be used to monitor or manage the upload.
   */
  @objc(putFile:) @discardableResult open func __putFile(from fileURL: URL) -> StorageUploadTask {
    return putFile(from: fileURL, metadata: nil, completion: nil)
  }

  /**
   * Asynchronously uploads a file to the currently specified `StorageReference`.
   * `putData` should be used instead of `putFile` in Extensions.
   * - Parameters:
   *   - fileURL: A URL representing the system file path of the object to be uploaded.
   *   - metadata: `StorageMetadata` containing additional information (MIME type, etc.)
   *       about the object being uploaded.
   *   - completion: A completion block that either returns the object metadata on success,
   *       or an error on failure.
   * - Returns: An instance of `StorageUploadTask`, which can be used to monitor or manage the upload.
   */
  @objc(putFile:metadata:completion:) @discardableResult
  open func putFile(from fileURL: URL,
                    metadata: StorageMetadata? = nil,
                    completion: ((_: StorageMetadata?, _: Error?) -> Void)?) -> StorageUploadTask {
    let putMetadata: StorageMetadata = metadata ?? StorageMetadata()
    if let path = path.object {
      putMetadata.path = path
      putMetadata.name = (path as NSString).lastPathComponent as String
    }
    let task = StorageUploadTask(reference: self,
                                 service: storage.fetcherServiceForApp,
                                 queue: storage.dispatchQueue,
                                 file: fileURL,
                                 metadata: putMetadata)
    startAndObserveUploadTask(task: task, completion: completion)
    return task
  }

  // MARK: - Downloads

  /**
   * Asynchronously downloads the object at the `StorageReference` to a `Data` instance in memory.
   * A `Data` buffer of the provided max size will be allocated, so ensure that the device has enough free
   * memory to complete the download. For downloading large files, `write(toFile:)` may be a better option.
   * - Parameters:
   *   - maxSize: The maximum size in bytes to download. If the download exceeds this size,
   *       the task will be cancelled and an error will be returned.
   *   - completion: A completion block that either returns the object data on success,
   *       or an error on failure.
   * - Returns: An `StorageDownloadTask` that can be used to monitor or manage the download.
   */
  @objc(dataWithMaxSize:completion:) @discardableResult
  open func getData(maxSize: Int64,
                    completion: @escaping ((_: Data?, _: Error?) -> Void)) -> StorageDownloadTask {
    let fetcherService = storage.fetcherServiceForApp
    let task = StorageDownloadTask(reference: self,
                                   service: fetcherService,
                                   queue: storage.dispatchQueue,
                                   file: nil)

    task.completionData = completion
    let callbackQueue = fetcherService.callbackQueue ?? DispatchQueue.main

    task.observe(.success) { snapshot in
      let error = self.checkSizeOverflow(task: snapshot.task, maxSize: maxSize)
      callbackQueue.async {
        if let completion = task.completionData {
          let data = error == nil ? task.downloadData : nil
          completion(data, error)
          task.completionData = nil
        }
      }
    }
    task.observe(.failure) { snapshot in
      callbackQueue.async {
        task.completionData?(nil, snapshot.error)
        task.completionData = nil
      }
    }
    task.observe(.progress) { snapshot in
      if let error = self.checkSizeOverflow(task: snapshot.task, maxSize: maxSize) {
        task.cancel(withError: error)
      }
    }
    task.enqueue()
    return task
  }

  /**
   * Asynchronously retrieves a long lived download URL with a revokable token.
   * This can be used to share the file with others, but can be revoked by a developer
   * in the Firebase Console.
   * - Parameter completion A completion block that either returns the URL on success,
   *     or an error on failure.
   */
  @objc(downloadURLWithCompletion:)
  open func downloadURL(completion: @escaping ((_: URL?, _: Error?) -> Void)) {
    let fetcherService = storage.fetcherServiceForApp
    let task = StorageGetDownloadURLTask(reference: self,
                                         fetcherService: fetcherService,
                                         queue: storage.dispatchQueue,
                                         completion: completion)
    task.enqueue()
  }

  #if compiler(>=5.5) && canImport(_Concurrency)
    /**
     * Asynchronously retrieves a long lived download URL with a revokable token.
     * This can be used to share the file with others, but can be revoked by a developer
     * in the Firebase Console.
     * - Throws: An error if the download URL could not be retrieved.
     * - Returns: The URL on success.
     */
    @available(iOS 13, tvOS 13, macOS 10.15, watchOS 8, *)
    open func downloadURL() async throws -> URL {
      return try await withCheckedThrowingContinuation { continuation in
        self.downloadURL { result in
          continuation.resume(with: result)
        }
      }
    }
  #endif // compiler(>=5.5) && canImport(_Concurrency)

  /**
   * Asynchronously downloads the object at the current path to a specified system filepath.
   * - Parameter fileURL A file system URL representing the path the object should be downloaded to.
   * - Returns An `StorageDownloadTask` that can be used to monitor or manage the download.
   */
  @objc(writeToFile:) @discardableResult
  open func write(toFile fileURL: URL) -> StorageDownloadTask {
    return write(toFile: fileURL, completion: nil)
  }

  /**
   * Asynchronously downloads the object at the current path to a specified system filepath.
   * - Parameters:
   *   - fileURL: A file system URL representing the path the object should be downloaded to.
   *   - completion: A closure that fires when the file download completes, passed either
   *       a URL pointing to the file path of the downloaded file on success,
   *       or an error on failure.
   * - Returns: A `StorageDownloadTask` that can be used to monitor or manage the download.
   */
  @objc(writeToFile:completion:) @discardableResult
  open func write(toFile fileURL: URL,
                  completion: ((_: URL?, _: Error?) -> Void)?) -> StorageDownloadTask {
    let fetcherService = storage.fetcherServiceForApp
    let task = StorageDownloadTask(reference: self,
                                   service: fetcherService,
                                   queue: storage.dispatchQueue,
                                   file: fileURL)

    if let completion = completion {
      task.completionURL = completion
      let callbackQueue = fetcherService.callbackQueue ?? DispatchQueue.main

      task.observe(.success) { snapshot in
        callbackQueue.async {
          task.completionURL?(fileURL, nil)
          task.completionURL = nil
        }
      }
      task.observe(.failure) { snapshot in
        callbackQueue.async {
          task.completionURL?(nil, snapshot.error)
          task.completionURL = nil
        }
      }
    }
    task.enqueue()
    return task
  }

  // MARK: - List Support

  /**
   * Lists all items (files) and prefixes (folders) under this `StorageReference`.
   *
   * This is a helper method for calling `list()` repeatedly until there are no more results.
   * Consistency of the result is not guaranteed if objects are inserted or removed while this
   * operation is executing. All results are buffered in memory.
   *
   * `listAll(completion:)` is only available for projects using Firebase Rules Version 2.
   *
   * - Parameter completion A completion handler that will be invoked with all items and prefixes under
   *       the current `StorageReference`.
   */
  @objc(listAllWithCompletion:)
  open func listAll(completion: @escaping ((_: StorageListResult?, _: Error?) -> Void)) {
    let fetcherService = storage.fetcherServiceForApp
    var prefixes = [StorageReference]()
    var items = [StorageReference]()

    weak var weakSelf = self

    var paginatedCompletion: ((_: StorageListResult?, _: Error?) -> Void)?
    paginatedCompletion = { (_ listResult: StorageListResult?, _ error: Error?) in
      if let error = error {
        completion(nil, error)
        return
      }
      guard let strongSelf = weakSelf else { return }
      guard let listResult = listResult else {
        fatalError("internal error: both listResult and error are nil")
      }
      prefixes.append(contentsOf: listResult.prefixes)
      items.append(contentsOf: listResult.items)

      if let pageToken = listResult.pageToken {
        let nextPage = StorageListTask(reference: strongSelf,
                                       fetcherService: fetcherService,
                                       queue: strongSelf.storage.dispatchQueue,
                                       pageSize: nil,
                                       previousPageToken: pageToken,
                                       completion: paginatedCompletion)
        nextPage.enqueue()
      } else {
        let result = StorageListResult(withPrefixes: prefixes, items: items, pageToken: nil)

        // Break the retain cycle we set up indirectly by passing the callback to `nextPage`.
        paginatedCompletion = nil
        completion(result, nil)
      }
    }

    let task = StorageListTask(reference: self,
                               fetcherService: fetcherService,
                               queue: storage.dispatchQueue,
                               pageSize: nil,
                               previousPageToken: nil,
                               completion: paginatedCompletion)
    task.enqueue()
  }

  #if compiler(>=5.5) && canImport(_Concurrency)
    /**
     * Lists all items (files) and prefixes (folders) under this StorageReference.
     *
     * This is a helper method for calling list() repeatedly until there are no more results.
     * Consistency of the result is not guaranteed if objects are inserted or removed while this
     * operation is executing. All results are buffered in memory.
     *
     * `listAll()` is only available for projects using Firebase Rules Version 2.
     *
     * - Throws: An error if the list operation failed.
     * - Returns: All items and prefixes under the current `StorageReference`.
     */
    @available(iOS 13, tvOS 13, macOS 10.15, watchOS 8, *)
    open func listAll() async throws -> StorageListResult {
      return try await withCheckedThrowingContinuation { continuation in
        self.listAll { result in
          continuation.resume(with: result)
        }
      }
    }
  #endif // compiler(>=5.5) && canImport(_Concurrency)

  /**
   * List up to `maxResults` items (files) and prefixes (folders) under this StorageReference.
   *
   * "/" is treated as a path delimiter. Firebase Storage does not support unsupported object
   * paths that end with "/" or contain two consecutive "/"s. All invalid objects in GCS will be
   * filtered.
   *
   * `list(maxResults:completion:)` is only available for projects using Firebase Rules Version 2.
   *
   * - Parameters:
   *   - maxResults: The maximum number of results to return in a single page. Must be greater
   *       than 0 and at most 1000.
   *   - completion: A completion handler that will be invoked with up to `maxResults` items and
   *       prefixes under the current `StorageReference`.
   */
  @objc(listWithMaxResults:completion:)
  open func list(maxResults: Int64,
                 completion: @escaping ((_: StorageListResult?, _: Error?) -> Void)) {
    if maxResults <= 0 || maxResults > 1000 {
      completion(nil,
                 NSError(domain: StorageErrorDomain,
                         code: StorageErrorCode.invalidArgument.rawValue,
                         userInfo: [NSLocalizedDescriptionKey:
                           "Argument 'maxResults' must be between 1 and 1000 inclusive."]))
    } else {
      let fetcherService = storage.fetcherServiceForApp
      let task = StorageListTask(reference: self,
                                 fetcherService: fetcherService,
                                 queue: storage.dispatchQueue,
                                 pageSize: maxResults,
                                 previousPageToken: nil,
                                 completion: completion)
      task.enqueue()
    }
  }

  /**
   * Resumes a previous call to `list(maxResults:completion:)`, starting after a pagination token.
   * Returns the next set of items (files) and prefixes (folders) under this `StorageReference`.
   *
   * "/" is treated as a path delimiter. Storage does not support unsupported object
   * paths that end with "/" or contain two consecutive "/"s. All invalid objects in GCS will be
   * filtered.
   *
   * `list(maxResults:pageToken:completion:)`is only available for projects using Firebase Rules
   * Version 2.
   *
   * - Parameters:
   *   - maxResults: The maximum number of results to return in a single page. Must be greater
   *     than 0 and at most 1000.
   *   - pageToken: A page token from a previous call to list.
   *   - completion: A completion handler that will be invoked with the next items and prefixes
   *     under the current StorageReference.
   */
  @objc(listWithMaxResults:pageToken:completion:)
  open func list(maxResults: Int64,
                 pageToken: String,
                 completion: @escaping ((_: StorageListResult?, _: Error?) -> Void)) {
    if maxResults <= 0 || maxResults > 1000 {
      completion(nil,
                 NSError(domain: StorageErrorDomain,
                         code: StorageErrorCode.invalidArgument.rawValue,
                         userInfo: [NSLocalizedDescriptionKey:
                           "Argument 'maxResults' must be between 1 and 1000 inclusive."]))
    } else {
      let fetcherService = storage.fetcherServiceForApp
      let task = StorageListTask(reference: self,
                                 fetcherService: fetcherService,
                                 queue: storage.dispatchQueue,
                                 pageSize: maxResults,
                                 previousPageToken: pageToken,
                                 completion: completion)
      task.enqueue()
    }
  }

  // MARK: - Metadata Operations

  /**
   * Retrieves metadata associated with an object at the current path.
   * - Parameter completion A completion block which returns the object metadata on success,
   *   or an error on failure.
   */
  @objc(metadataWithCompletion:)
  open func getMetadata(completion: @escaping ((_: StorageMetadata?, _: Error?) -> Void)) {
    let fetcherService = storage.fetcherServiceForApp
    let task = StorageGetMetadataTask(reference: self,
                                      fetcherService: fetcherService,
                                      queue: storage.dispatchQueue,
                                      completion: completion)
    task.enqueue()
  }

  #if compiler(>=5.5) && canImport(_Concurrency)
    /**
     * Retrieves metadata associated with an object at the current path.
     * - Throws: An error if the object metadata could not be retrieved.
     * - Returns: The object metadata on success.
     */
    @available(iOS 13, tvOS 13, macOS 10.15, watchOS 8, *)
    open func getMetadata() async throws -> StorageMetadata {
      return try await withCheckedThrowingContinuation { continuation in
        self.getMetadata { result in
          continuation.resume(with: result)
        }
      }
    }
  #endif // compiler(>=5.5) && canImport(_Concurrency)

  /**
   * Updates the metadata associated with an object at the current path.
   * - Parameters:
   *   - metadata: A `StorageMetadata` object with the metadata to update.
   *   - completion: A completion block which returns the `StorageMetadata` on success,
   *     or an error on failure.
   */
  @objc(updateMetadata:completion:)
  open func updateMetadata(_ metadata: StorageMetadata,
                           completion: ((_: StorageMetadata?, _: Error?) -> Void)?) {
    let fetcherService = storage.fetcherServiceForApp
    let task = StorageUpdateMetadataTask(reference: self,
                                         fetcherService: fetcherService,
                                         queue: storage.dispatchQueue,
                                         metadata: metadata,
                                         completion: completion)
    task.enqueue()
  }

  #if compiler(>=5.5) && canImport(_Concurrency)
    /**
     * Updates the metadata associated with an object at the current path.
     * - Parameter metadata A `StorageMetadata` object with the metadata to update.
     * - Throws: An error if the metadata update operation failed.
     * - Returns: The object metadata on success.
     */
    @available(iOS 13, tvOS 13, macOS 10.15, watchOS 8, *)
    open func updateMetadata(_ metadata: StorageMetadata) async throws -> StorageMetadata {
      return try await withCheckedThrowingContinuation { continuation in
        self.updateMetadata(metadata) { result in
          continuation.resume(with: result)
        }
      }
    }
  #endif // compiler(>=5.5) && canImport(_Concurrency)

  // MARK: - Delete

  /**
   * Deletes the object at the current path.
   * - Parameter completion A completion block which returns a nonnull error on failure.
   */
  @objc(deleteWithCompletion:)
  open func delete(completion: ((_: Error?) -> Void)?) {
    let fetcherService = storage.fetcherServiceForApp
    let task = StorageDeleteTask(reference: self,
                                 fetcherService: fetcherService,
                                 queue: storage.dispatchQueue,
                                 completion: completion)
    task.enqueue()
  }

  #if compiler(>=5.5) && canImport(_Concurrency)
    /**
     * Deletes the object at the current path.
     * - Throws: An error if the delete operation failed.
     */
    @available(iOS 13, tvOS 13, macOS 10.15, watchOS 8, *)
    open func delete() async throws {
      return try await withCheckedThrowingContinuation { continuation in
        self.delete { error in
          if let error = error {
            continuation.resume(throwing: error)
          } else {
            continuation.resume()
          }
        }
      }
    }
  #endif // compiler(>=5.5) && canImport(_Concurrency)

  // MARK: - NSObject overrides

  @objc override open func copy() -> Any {
    return StorageReference(storage: storage, path: path)
  }

  @objc override open func isEqual(_ object: Any?) -> Bool {
    guard let ref = object as? StorageReference else {
      return false
    }
    return storage == ref.storage && path == ref.path
  }

  @objc override public var hash: Int {
    return storage.hash ^ path.bucket.hashValue
  }

  @objc override public var description: String {
    return "gs://\(path.bucket)/\(path.object ?? "")"
  }

  // MARK: - Internal APIs

  /**
   * The current path which points to an object in the Google Cloud Storage bucket.
   */
  internal let path: StoragePath

  override internal init() {
    storage = Storage.storage()
    let storageBucket = storage.app.options.storageBucket!
    path = StoragePath(with: storageBucket)
  }

  init(storage: Storage, path: StoragePath) {
    self.storage = storage
    self.path = path
  }

  /**
   * For maxSize API, return an error if the size is exceeded.
   */
  private func checkSizeOverflow(task: StorageTask, maxSize: Int64) -> NSError? {
    if task.progress.totalUnitCount > maxSize || task.progress.completedUnitCount > maxSize {
      return StorageErrorCode.error(withCode: .downloadSizeExceeded,
                                    infoDictionary: [
                                      "totalSize": task.progress.totalUnitCount,
                                      "maxAllowedSize": maxSize,
                                    ])
    }
    return nil
  }

  private func startAndObserveUploadTask(task: StorageUploadTask,
                                         completion: ((_: StorageMetadata?, _: Error?) -> Void)?) {
    if let completion = completion {
      task.completionMetadata = completion
      let callbackQueue = storage.fetcherServiceForApp.callbackQueue ?? DispatchQueue.main

      task.observe(.success) { snapshot in
        callbackQueue.async {
          task.completionMetadata?(snapshot.metadata, nil)
          task.completionMetadata = nil
        }
      }
      task.observe(.failure) { snapshot in
        callbackQueue.async {
          task.completionMetadata?(nil, snapshot.error)
          task.completionMetadata = nil
        }
      }
    }
    task.enqueue()
  }
}
